Variable indication control signal

ABSTRACT

A traffic signal, appearing from a distance as a simple warning light, converts progressively into an instructional signal as viewed during the approach.

United States Patent Inventor Gunnar R. Ljungkull White Bear Lake, Minn.

App]. No. 853,443

Filed Aug. 27, 1969 Patented Nov. 2,1971

Assignee Minnesota Mining and Manufacturing Company Saint Paul, Minn.

VARIABLE INDICATION CONTROL SIGNAL 1 1 Claims, 8 Drawing Figs.

Int. Cl B601 1/00 Field of Search 340/107, 110, 84; 240/4633, 46.53;40/l.6, 97, 36, 124.1,

[56] References Cited UNITED STATES PATENTS D.64,322 3/1924 Petersen340/84 2,540,389 2/1951 Fowler 340/84 X Primary Examiner-John W.Caldwell Assistant Examiner-William M. Wannisky Attorney-Kinney,Alexander, Sell, Steldt & Delahunt ABSTRACT: A traffic signal, appearingfrom a distance as a simple warning light, converts progressively intoan instructional signal as viewed during the approach.

VARIABLE INDICATION t'JONTROL SIGNAL This invention relates primarily tothe instruction and control of vehicular and other moving traffic and tonovel signal lights for use therein. One illustrative embodiment is anarrow turn signal for instructing approaching traffic to make theindicated turn; and the invention, while not in any way restrictedthereto, will for convenience be described primarily in terms of a lightsignal showing an illuminated arrow as an instructional area on a largerdisplay surface.

Lighted-arrow displays are ordinarily provided by masking the backgroundareas so that light from the source passes through only the arrowportion. The resultant restriction in lighted area makes the displaydifficult to see at a distance.

The present invention on the contrary provides for illumination of thefull area of the viewing surface as seen from a distance, while causingprogressively greater blocking of light from the background areas to aviewer approaching the device. As a result, the signal is first seen asa relatively large and substantially uniformly illuminated area, therebycapturing the attention of the viewer as well as suggesting cautionduring the approach. At closer distances the amount of light reachingthe viewer from the instructional area, i.e. the arrow symbol, remainssubstantially constant; but the light from the background areas isprogressively reduced, so that from posi tions on the highway relativelyclose to the signal only the symbol appears lighted.

It will be appreciated that a reverse situation may also occur, whereinthe light from the arrow or other indicia is progressively reduced whilethe surrounding areas continue to appear fully illuminated; in whichcase the arrow becomes the background area. Similarly, a moving signalapproaching a stationary or moving observer is to be considered the fullequivalent ofan observer approaching a stationary signal.

In the drawing,

FIG. 1 is a front elevation, and FIG. 2 is a cross-sectional elevationtaken approximately at section 2-2 of FIG. 1, of one form of signal;

FIG. 3 is a schematic illustration showing the signal of FIGS. 1 and 2in operation at an intersection and indicating the appearance of thedisplay surface to an observer at each of three locations along thetraffic lane;

FIG. 4 is a side elevation, partly in section, of an attachment for acommon form of highway signal, the latter being schematically indicatedin dotted outlines,

FIG. 5 is a side elevation in section showing an alternative andpreferred form of a portion of the attachment of FIG. 4, and

FIGS. 6-8 represent illustrative alternative forms of control panelsshown schematically in cross section.

Hereinafter, any references to horizontal and vertical positions arewith reference to signal lights as ordinarily mounted and as illustratedin the accompanying drawing. Where the device is to be used in adifferent situation or position, correspondingly different relationshipswill be understood to apply.

The signal device 10 of FIGS. 1 and 2 is comprised of an internallyspecularly reflective generally parabolic housing 11 fitted with alight-transmitting light-scattering plate or lens 12 and a light source13. A transparent control panel 14 is placed over the forward face ofthe lens. It consists of a central clear transparent indicia portion 15,here shown in the shape of a directional arrow, and a surroundingportion 16 containing a number of uniformly spaced thin narrow louvers17 disposed in parallel horizontal planes.

FIG. 3 illustrates the placement of the traffic control device 10adjacent a highway intersection 30, in this instance with the deviceabove and to one side of the line of traffic, and disposed so as todirect traffic approaching the intersection along a lane 31. From adistance, e.g. SOC-1,000 feet from the intersection, a driver will seethe signal as an area 32 of small size and uniform light intensity. Asthe driver nears the inter section the apparent size of the signalincreases and the intensity at the central portion remains much thesame, but the outer or background areas begin to lose intensity as shownat 33 representing a position at, for example, about 300 feet from thesignal. Further advance toward the intersection results in progressivereduction in background intensity until at position 345, somewhat inadvance of the entrance to the right turn lane 35, only the centralarrow appears lighted.

In the situation pictured in FIG. 3, with the control device very closeto the line of traffic, the louvers are disposed with both theirlongitudinal and transverse axis in approximately the horizontalposition. With the control device located at some lateral distance fromthe line of traffic, it is sometimes found necessary to place thelouvers with their longitudinal axis at some angle with the horizontalfor obtaining maximum light-controlling effectiveness along thepertinent viewing path. Maximum effectiveness is ordinarily obtained byso placing the louvers that a line connecting the signal and theobserver approaches the perpendicular to the parallel planes of thelouvers as the observer, proceeding along said path, approaches a pointadjacent an edge of the panel. Incorporation of more than one set ofparallel louvers arranged at different angles, for example at rightangles to each other, is also possible and may serve to further extendthe usefulness of the device, but is ordinarily not required.

FIG. 4 illustrates a modification wherein the louvers 47 are disposedwith their lateral axis at an upward slant from the light source whiletheir longitudinal axis remains horizontal. The control panel 44 isvertically supported within a hood 40 by means of flanges 41. The hoodis attached to a standard highway signal 43, here indicatedschematically in dotted outline, by suitable mounting means such asbolts 48. The louvered area surrounds a clear indicia-forming area 35.

The device illustrated in FIG. 5 is. designed to be inserted within thehood 40 of FIG. 4 when the latter forms a permanent part of aconventional signal installation, i.e. in the absence of flanges M andpanel 44. It consists of a tubular body 50 in which a control panel S4is mounted between flanges 51 and at an angle of about l0 to about 15degrees with the vertical, as represented by the position shown forpanel 44 in FIG. 4. The louvers 57 are perpendicular to the surface ofthe panel, so that in the signal installation their lateral axis is atabout l0l5 degrees to the horizontal while their longitudinal axis willordinarily remain substantially horizontal. A directional signal isprovided by the clear portion 55. The control panel of FIG. 5 mayalternatively be inserted directly in the hood 40 of FIG. 4 in place ofthe panel 44.

The structure may be designed to provide a signal in color, for exampleby employing a separate color filter or a colored lens or control panel.The control panel may itself be properly contoured to serve as a lens.For some purposes colored semitransparent louvers may be used. Theinstruction or indicia-forming areas are conveniently prepared byremoval of the corresponding portion of a uniformly louvered panel, theremoved portion being replaced if desired with a clear or coloredlight-transmitting segment of a similar panel but free of louvers.

Some examples of other control panel structures are shown in FIGS. 6-8.Panel 64 of FIG. 6 consists of a louvered central layer 66, from whichportions have been removed to provide indicia-forming openings 65 andthin transparent outer layers 61, 62 covering and unifying the entirepanel. In the panel 74 of FIG. 7 the outer transparent plastic :films71, 72 are pressed and sealed together within the indicia-formingopenings 75 of the louvered panel 76. A single outer transparent pane orfilm 81 is bonded to the louvered panel 86 containing a louver-freeinsert 82 to form the panel 84 of FIG. 8.

It is preferred to make the louvers as thin as possible so as to losethe least amount of light when viewed at a distance and with the lightrays substantially parallel to the width of the louvers. One convenientform of louvered panel consists of a stack of bonded strips of clearthin plastic, e.g. polycarbonate or cellulose acetate butyrate,separated by single opaque layers of light-absorptive black paint, thepanel being prepared by skiving from a precombined stack of paintedplastic sheets, for example as described in Astima US. Pat. No.2,053,173. Combining the louvered panel with transparent surface filmsprotects and further unifies the structure and serves as a convenientway of eliminating any light-difiusing surface roughness, but is notessential.

Skiving at right angles to the layers of painted plastic film produces acontrol panel for use as shown in FIG. 2 wherein the widths and lengthsof the louvers are substantially horizontal. Three-mil transparent filmcoated with about one-half mil of black paint, bonded together in apanel of 30-mil thickness, has proven effective for such purposes.Slanted louvers as shown in the panel 44 of FIG. 4 may be obtained inthe same manner by skiving at a greater or lesser angle, in this casepreferably using somewhat thicker plastic film, for example lO-mil film,and skiving to a panel thickness of 20 mils. The specific angle, width,and spacing of the louvers, and their angle of maximum effectiveness,are selected with a view to providing full illumination at a distancewhile exhibiting substantially complete cutoff when viewed from thedesired closeup position.

An appreciable amount of side glow may be experienced with signalswherein the louvers are disposed as shown in FIG. 1, since a smallamount of light is reflected from the flat surfaces of the louvers. Theside glow is typically seen from positions near the edge of the signal,as at position 34 of FIG. 3, as an indistinct second image correspondingto the clear area 15 but slightly displaced therefrom. Although maximumlight transmission is obtainable with such a control panel, the sideglow may in some instances be found disturbing. The condition may becorrected by tilting the louvers as in the device of FIG. 4, but at theexpense of a considerable further reduction in viewing intensity. Thetilted louvers receive substantially no light on their lower surfaces sothat no light is reflected therefrom to cause observable glow atpositions beneath or to the side of the signal; but the upper surfaces,being in the path of the beam, absorb or reflect a considerableproportion of the total light and thus reduce the useful output to theviewing area. The arrangement shown in connection with FIG. 5 is foundto be equally as effective in eliminating side glow as that of FIG. 4,while providing unexpectedly high light intensity within the viewingzone. In this arrangement the lower surface of the louvers is shieldedfrom the light rays, which however are refracted upwardly at theair-plastic interface. Most of the rays therefore do not touch thelouver upper surfaces, but continue through the panel. Reverserefraction at the plasticair interface then returns these rays to theiroriginal direction. For maximum transmission, the louvers may be placedat a slight angle to the perpendicular, so as to be parallel to therefracted rays.

In a comparative test using 20-mil panels containing parallel half-millouvers spaced mils apart, the intensity of the light beam measured at apoint directly in front of the signal device is found to be at leasthalf again as great for a structure containing louvers perpendicularlydisposed within a slanted panel as in FIG. 5 as it is for a structurecontaining louvers disposed at an angle within a vertical panel as inFIG. 4. In both cases, side glow is virtually eliminated.

It will be appreciated that signal devices as here described may be usedin conjunction with various other control devices as required for anyparticular traffic control situation. Merely as illustrative, the lightsource may be cycled between on and Off condition in conformity with theoperation of additional signals by means of conventional timing andswitching mechanism, not shown. The invention provides an illuminatedtraffic control device which offers maximum visibility at maximumdistances and converts to positive instructional capability duringapproach, while being of simple and sturdy construction and requiring nomotors, shutters or other moving parts.

What is claimed is as follows:

1. A visual control panel having light-transmitting indicia andbackground areas and including narrow louver means within saidbackground areas for progressively reducing the pro ortion oftransmitted light reaching a viewing station from sat background areasas said station approaches a point adjacent an edge of said panel.

2. The control panel of claim 1 wherein said louver means are thin,parallel, and nontransparent, and are uniformly spaced throughout saidbackground areas.

3. An illuminating device comprising the control panel of claim 2 incombination with light source means for supplying light therethrough.

4. The device of claim 3 wherein said source means is a traffic signalcomprising a light source, a specular reflector, and a light-scatteringlens.

5. The device of claim 3 wherein said louvers are disposed with theirlateral axis at an upward slant from the light source.

6. The device of claim 3 wherein said panel is slanted upwardly towardsaid light source.

7. The device of claim 6 wherein said louvers are disposed with theirlateral axis perpendicular to said panel.

8. The method of alerting and informing traffic approaching a controlpoint comprising placing, at a viewing location adjacent said controlpoint, a control device comprising a visual control panel havinglight-transmitting indicia and background areas and including narrowlouver means within said background areas in combination with lightsource means for supplying light therethrough, and with said louversdisposed at the angle of maximum light-controlling effectiveness for theapproaching traffic.

9. The method of providing a directional traffic signal, comprisingplacing a directional control panel, having light-transmitting indiciaand background areas and including thin, narrow, parallel,nontransparent, uniformly spaced louver means within said backgroundareas, and having said image areas designed to provide the desireddirectional signal, directly in front of a nondirectional traffic signalwhich supplies light over the entire area of said panel and with saidlouvers disposed at the angle of maximum effectiveness.

10. The method of claim 9 wherein said panel is placed at an upwardslant toward said light source and said louvers are disposed with theirlateral axis perpendicular to the surface of said panel.

11. The panel of claim 2 wherein said louver means are not greater thanabout 0.03 inch in width and are spaced apart not more than about 0.01inch.

1. A visual control panel having light-transmitting indicia and background areas and including narrow louver means within said background areas for progressively reducing the proportion of transmitted light reaching a viewing station from said background areas as said station approaches a point adjacent an edge of said panel.
 2. The control panel of claim 1 wherein said louver means are thin, parallel, and nontransparent, and are uniformly spaced throughout said background areas.
 3. An illuminating device comprising the control panel of claim 2 in combination with light source means for supplying light therethrough.
 4. The device of claim 3 wherein said source means is a traffic signal comprising a light source, a specular reflector, and a light-scattering lens.
 5. The device of claim 3 wherein said louvers are disposed with their lateral axis at an upward slant from the light source.
 6. The device of claim 3 wherein said panel is slanted upwardly toward said light source.
 7. The device of claim 6 wherein said louvers are disposed with their lateral axis perpendicular to said panel.
 8. The method of alerting and informing traffic approaching a control point comprising placing, at a viewing location adjacent said control point, a control device comprising a visual control panel having light-transmitting indicia and background areas and including narrow louver means within said background areas in combination with light source means for supplying light therethrough, and with said louvers disposed at the angle of maximum light-controlling effectiveness for the approaching traffic.
 9. The method of providing a directional traffic signal, comprising placing a directional control panel, having light-transmitting indicia and background areas and including thin, narrow, parallel, nontransparent, uniformly spaced louver means within said background areas, and having said image areas designed to provide the desired directional signal, directly in front of a nondirectional traffic signal which supplies light over the entire area of said panel and with said louvers disposed at the angle of maximum effectiveness.
 10. The method of claim 9 wherein said panel is placed at an upward slant toward said light source and said louvers are disposed with their lateral axis perpendicular to the surface of said panel.
 11. The panel of claim 2 wherein said louver means are not greater than about 0.03 inch in width and are spaced apart not more than about 0.01 inch. 